Three aspects of the periovulatory interval will be studied in the rabbit: 1) follicle wall disruption (ovulation); 2) oocyte maturation (nuclear and cytoplasmic); and 3) corpus luteum formation. An in vitro perfused ovary preparation will be used to isolate the ovary from systemic influences, regulate the contents of the perfusion fluid, and determine constituents of the effluent during the periovulatory interval. Interrelationships among ovarian prostaglandins, enzymatic activity and follicle rupture will be explored in vivo and in vitro using specific plasminogen activators (streptokinase, tPA) and enzyme inhibitors (tAMCHA, epsilon-amino caproic acid, aprotinin, and alpha 2-macroglobulin) as well as prostaglandins (PGF2 alpha, PGI2) and the prostaglandin synthetase inhibitor, indomethacin. The role of the ovarian renin- angiotensin system during the periovulatory interval will be studied using combinations of angiotensin II and its antagonists and angiotensin converting enzyme inhibitors. The effects of estradiol, prolactin, and epidermal growth factor (EGF) on attainment of nuclear and cytoplasmic maturation of oocytes will be investigated using in vitro ovulated oocytes and cultured oocyte-cumulus complexes inseminated in vitro and followed to the blastocyst stage. The site of action of estradiol and prolactin on oocyte cytoplasmic maturation will be investigated by means of pronuclear and cytoplasmic transplantation. The perfusion system will be used to investigate structure/function relationships during the process of conversion of the ruptured follicle into a corpus luteum. The effect of preovulatory influences on corpus luteum formation will also be studied using inhibitors of steroidogenesis, an estrogen antagonist, and EGF. Transmission electron microscopy will be employed to study ultrastructure of the follicle wall in experiments designed to elucidate the mechanism(s) of ovulation and corpus luteum formation. Casts of perifollicular vessels will be examined by scanning electron microscopy for periovulatory vascular changes. Estradiol, progesterone, prostaglandins, and angiogenic activity will be assayed in the venous effluent from ovarian perfusion experiments throughout the periovulatory interval. An in depth knowledge of the periovulatory interval (follicle rupture, oocyte maturation, and corpus luteum formation) is critical for developing new methods for improving reproductive performance and for achieving fertility control.